On October 28, 2017 8:10:34 AM EDT, Rich <centos at foxengines.net> wrote: >Hi, > >On Fri, Oct 27, 2017 at 05:27:22PM -0400, H wrote: >> What is the best tool to compare file hashes in two different >drives/directories such as after copying a large number of files from >one drive to another? I used cp -au to copy directories, not rsync, >since it is between local disks. >[snip] >> Are there other tools for this automatic compare where I am really >looking for a list of files that exist in only one place or where >checksums do not match? > >rsync obviously offers the 'exist in only one place' feature but also >offers checksum comparisons (in version 3 and higher, I understand)... > >-c, --checksum > This changes the way rsync checks if the files have been changed > and are in need of a transfer. Without this option, rsync uses > a "quick check" that (by default) checks if each file’s size and > time of last modification match between the sender and receiver. > This option changes this to compare a 128-bit checksum for each > file that has a matching size. Generating the checksums means > that both sides will expend a lot of disk I/O reading all the > data in the files in the transfer (and this is prior to any > reading that will be done to transfer changed files), so this > can slow things down significantly. > > The sending side generates its checksums while it is doing the > file-system scan that builds the list of the available files. > The receiver generates its checksums when it is scanning for > changed files, and will checksum any file that has the same size > as the corresponding sender’s file: files with either a changed > size or a changed checksum are selected for transfer. > > Note that rsync always verifies that each transferred file was > correctly reconstructed on the receiving side by checking a > whole-file checksum that is generated as the file is trans‐ > ferred, but that automatic after-the-transfer verification has > nothing to do with this option’s before-the-transfer "Does this > file need to be updated?" check. > > For protocol 30 and beyond (first supported in 3.0.0), the > checksum used is MD5. For older protocols, the checksum used is > MD4. > > >Rich. >_______________________________________________ >CentOS mailing list >CentOS at centos.org >https://lists.centos.org/mailman/listinfo/centos Thank you, this time I used diff.